Hypothesis: ADPKD children with elevated blood pressures who are treated with ACE inhibitors will have less stuctural progression of renal disease than untreated controls. Control of blood pressure is also anticipated to reduce in-increases in left ventricular mass and microalbuminuria. Study Design: Renal volume will be measured at baseline and annually for 3 years in children with ADPKD who have been randomized into treatment and nontreatment arms. The resulting data will be studied using a mixed-effects modelling approach.